Showing papers in "Human Biology in 1994"

Signature of ancient population growth in a low-resolution mitochondrial DNA mismatch distribution.

Abstract: A mismatch distribution is a tabulation of the number of pairwise differences among all DNA sequences in a sample. In a population that has been stationary for a long time these distributions from nonrecombinant DNA sequences become ragged and erratic, whereas a population that has been growing generates mismatch distributions that are smooth and have a peak. The position of the peak reflects the time of the population growth. The signature of an ancient population expansion is apparent even in the low-resolution mtDNA typings described by Merriwether et al. (1991). The smoothness of the mismatch distribution, an indicator of population expansion, is hardly affected by population structure, whereas mean sequence divergence increases in a pooled sample from highly isolated subpopulations.

Effects of maternal smoking on adverse pregnancy outcomes: examination of the criteria of causation.

Abstract: Smoking during pregnancy has been associated with many adverse pregnancy outcomes. However, debate continues about whether smoking causes these outcomes. This review of the criteria of causation found that the relative risk of having a low-birth-weight baby is nearly doubled in women who smoke during pregnancy compared with nonsmoking women and that the relative risks of spontaneous abortion and perinatal and neonatal mortality are increased by about one-third. The magnitude of the long-term effects of maternal smoking on the physical and mental development of the offspring is small but measurable. The epidemiologic evidence associating maternal smoking with major adverse pregnancy outcomes in prospective and case-control studies displays a high degree of consistency. A dose-response gradient for smoking during pregnancy has not been clearly shown in relation to perinatal and neonatal mortality. However, there is strong support for a dose-response gradient in relation to low birth weight and spontaneous abortion and moderate support for long-term developmental effects. Although a biological causal mechanism has not been clearly delineated, considerable evidence indicates that the chemicals in tobacco smoke are capable of producing deleterious changes in the placenta and fetus.

Mismatch distributions of mtDNA reveal recent human population expansions.

Abstract: Although many genetic studies of human evolution have tried to make distinctions between the replacement and the multiregional evolution hypotheses, current methods and data have not resolved the issue. However, new advances in nucleotide divergence theory can complement these investigations with a description of human demographic behavior during the late Middle and Upper Paleolithic (approximately the last 250,000 years). Restriction fragment length polymorphism (RFLP) and DNA sequence analyses of human mitochondrial DNAs (mtDNAs) from 25 ethnic and racial groups indicate that significant expansions occurred during the late Middle and Upper Paleolithic in 23 of the 25 populations examined. Estimates for the individual group expansion times are consistently less than 100,000 years ago with a mean expansion time of approximately 40,000 years ago. The dramatic expansions suggested by these data occurred well after modern human anatomy appeared, approximately 100,000 years ago, but are concordant with archeological evidence for the expansion of modern human technology, approximately 50,000 years ago.

Polynesian mitochondrial dnas reveal three deep maternal lineage clusters

Abstract: The 4000-year-old human population expansion into Remote Oceania has been studied from a variety of genetic perspectives. Here, we report the discovery that Polynesians, traditionally considered to be a single cohesive linguistic and cultural unit, exhibit at least three distinct mitochondrial DNA (mtDNA) groups that probably shared a common maternal ancestor more than 85,000 years ago. The major lineage groups were first identified by PCR amplification of the mitochondrial region V deletion marker, known to be present at high frequency in Polynesian populations. Sequence analysis of mtDNA hypervariable control regions reveals a surprising number of lineages in Polynesia. We also note high sequence divergence between lineage groups deleted and not deleted in region V. Major group I lineages are common in Remote Oceania and include about 95% of the Native Hawaiian, 90% of the Samoan, and 100% of the Tongan donors in our sample. They contain the region V deletion and generally share three control region transition substitutions. This group also contains non-Polynesian individuals, such as Indonesians, Native Americans, Micronesians, Malaysians, Japanese, and Chinese. The group I Polynesians differ by 4.4% in sequence identity from major lineage group II Polynesians, who do not have the region V deletion and who share among themselves four distinct single-base substitutions. Group II individuals are seen at low frequency (< 10%) in Hawaii, Samoa, and the Cook Islands and may represent the predominant maternal lineage group of Papuan Melanesia. Major lineage group III, not found in Hawaii, tentatively links Samoa to Indonesia. Our observation of deep maternal genetic branches in Polynesia today confirms the notion that during the colonization of the Pacific, mainland Asian immigrants mixed with Melanesian peoples already inhabiting Near Oceania and carried a complex assortment of maternal genotypes derived from two distinct geographic sources to isolated island archipelagoes.

mtDNA variation in the Chibcha Amerindian Huetar from Costa Rica.

Abstract: Articulo cientifico -- Universidad de Costa Rica, Instituto de Investigaciones en Salud. 1994

Genetic and environmental correlations between obesity and body fat distribution in adult male twins

Abstract: Genetic and environmental correlations between measures of obesity [body mass index (BMI)] and body fat distribution [waist/hip ratio (WHR) and subscapular/triceps ratio (SSTR)] were examined in 133 monozygotic and 129 dizygotic pairs of elderly white male twins, age 59 to 70 years, participating in the third cardiovascular examination of the National Heart, Lung, and Blood Institute Twin Study. The BMI, WHR, and SSTR fat measures were significantly correlated in these twins, with BMI more closely related to WHR (r = 0.52) than to SSTR (r = 0.18), and the WHR-SSTR association intermediate (r = 0.27). Multivariate genetic analyses of the three indexes using the LISREL modeling approach indicated a significant heritable component for each fatness variable, h2 = 0.66, 0.46, and 0.25 for BMI, WHR, and SSTR, respectively, and a significant correlation between genetic influences on BMI and WHR (genetic r = 0.51). The common genetic component accounted for 54% of the observed BMI-WHR correlation, suggesting that overall obesity and abdominal adiposity distribution are mediated to some extent by similar genetic influences. The genetic correlations between SSTR and BMI and between SSTR and WHR were not significantly different from zero, suggesting that genetic influences on skinfold distribution are independent of those on abdominal body fat and overall obesity. The genetic findings support the hypothesis that the WHR and SSTR indexes do not assess the same dimensions of fat patterning.

Distribution of the 9-bp mitochondrial DNA region V deletion among North American Indians.

Abstract: The deletion of a 9-bp segment from the intergenic region between the mtDNA cytochrome oxidase II gene and the lysine tRNA gene has been documented mainly in individuals of East Asian ancestry and in individuals from East Asian-derived populations (e.g., Polynesia). Among Native Americans the deletion is absent among Eskimos and northern Na-Dene populations and present among most Amerind populations [sensu Greenberg (1987); i.e., all Native Americans except Eskimo-Aleut and Na-Dene] that have been studied. To better characterize the frequency and distribution of the 9-bp deletion in North America, we surveyed more than 400 individuals from 59 tribes representing a variety of linguistic groups. The absence of the deletion among Eskimo and northern Na-Dene populations is confirmed. Among Amerind groups the deletion is present in all groups represented by more than six individuals. The geographic distribution of the frequencies of the deletion appears to be clinal in North America. The deletion is absent in the Artic and Subartic and reaches its highest frequency in the Southwest. This distribution is consistent with the hypothesis that the ancestors of the Amerinds and Na-Dene arrived in the New World by means of separate migrations. The presence of the 9-bp deletion in high frequencies in all the major linguistic groups in the Southwest suggests that migration among tribes was common.

DNA polymorphisms at the lipoprotein lipase gene and their association with quantitative variation in plasma high-density lipoproteins and triacylglycerides

Abstract: Lipoprotein lipase (LPL) plays a critical role in the metabolism of lipoproteins because this enzyme hydrolyzes the triacylglycerides in chylomicrons and very low density lipoproteins. This process influences the production of high-density lipoprotein (HDL), which takes up tissue cholesterol for transport to the liver for excretion. Accordingly, LPL qualifies as a candidate gene for understanding lipid metabolic disorders and atherosclerosis. Studies on the relationship between genetic variation at the LPL locus and lipid phenotypes have produced equivocal results to date. To help clarify this issue, we investigated 144 outwardly healthy male Mediterranean migrants (from Italy and Greece), age between 40 and 70 years and resident in Australia, for associations between two common LPL restriction site polymorphisms and the following lipid and lipoprotein phenotypes: total plasma cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triacylglycerides. A series of analysis of variance tests, controlling for age, body mass index, and ethnicity, showed that the HindIII polymorphism at the LPL locus is significantly associated with both triacylglyceride and HDL cholesterol concentrations in this sample. The PvUII polymorphism, however, showed no association with any lipid. Kruskal-Wallis tests confirmed the significance of the associations between the HindIII RFLP and both HDL (p = 0.008) and triacylglycerides (p = 0.03). When the sample was subdivided into subjects who exhibited primary hypertriacylglyceridemia and normolipidemics, a significant difference was observed in the frequency of HindIII (p < 0.05) but not PvuII genotypes. HindIII heterozygotes (H1,H2) were least and H2,H2 individuals were most at risk for triacylglyceridemia. Examination of the normolipidemic sample revealed some evidence for an independent effect of the PvuII polymorphism on both LDL cholesterol and total cholesterol levels.

Anthropological approach to the heterogeneity of beta-thalassemia mutations in northern Africa.

Abstract: Results of an epidemiological survey for beta-thalassemic defects involving 239 chromosomes in Algeria are analyzed in relation to the geographic and historical background of the country and are compared with published series for the Tunisian population Four common mutations account for 81% of the chromosomes, but 13 other defects have been found, illustrating the highly heterogeneous nature of the disease in the northern African countries of the Maghreb The high frequency of homozygous cases reflects the endogamous social structure of these populations Distribution of the mutations and linkage to specific RFLP haplotypes provide information concerning their origin and date of introduction in good correlation with the anthropological history of Algeria

Fitness of twinning.

Abstract: On the basis of a family reconstitution of the rural Krummhorn population (Ostfriesland, Germany) of the eighteenth and nineteenth centuries, we pursued the question of to what extent the birth of twins contributed to the reproductive fitness of their mothers. The twinning rate was 16.2/1000; the secondary sex ratio among twins was 0.93, and it was 1.16 among their singleton siblings. Mothers of twins were older, had a longer generative life phase, and achieved higher age-specific fertility rates with shorter birth intervals. Parity effects on twinning tendency could not be detected. Twin maternities caused reproductive costs, namely, increased maternal, infant, and child mortality and obviously higher intrafamilial competition, because adult twins had fewer local marriage chances and to a higher degree were forced to emigrate. These reproductive disadvantages mean that the productivity of a male pair of twins, as measured by the number of live-born grandchildren, is clearly less than the productivity of a single boy. On the other hand, the birth of a female pair of twins led to more live-born grandchildren than the birth of a single girl. In sum, mothers of twins achieved greater reproductive success, with 13.5% more live-born grandchildren, than mothers of singletons only. The results are discussed against the background of Anderson's (1990) error hypothesis of twinning.

Polymorphisms of the gene coding for the cholesteryl ester transfer protein and plasma lipid levels in Italian and Greek migrants to Australia.

Abstract: The relation between TaqI restriction fragment length polymorphisms (RFLPs) of the cholesteryl ester transfer protein (CETP) gene and plasma lipid and lipoprotein phenotypes was investigated in a sample of Italian and Greek migrants of both sexes, age 40-69 years. Italians display significantly higher mean triglyceride and lower mean high-density lipoprotein (HDL) cholesterol levels than Greeks. Greek females have significantly higher HDL cholesterol than Greek males, and Italian females have significantly higher low-density lipoprotein (LDL), HDL, and total cholesterol than Italian males. The differences in RFLP allele frequencies between the two ethnic groups and sexes are insignificant. Multivariate analyses show that in the Greek sample the TaqI B RFLP of the CETP gene has a highly significant effect on HDL cholesterol levels regardless of sex and that the TaqI A polymorphism has a significant effect on HDL levels in females but modulates LDL cholesterol concentrations in males. Among Italians, with the sexes considered separately or combined, no such effects of the CETP TaqI polymorphisms are detected. Kruskal-Wallis tests detected associations between the TaqI B polymorphism in all Greek samples but not in the Italian samples. Genotype CETP*B2 exhibits significantly higher HDL cholesterol concentrations than either of the other two TaqI B genotypes, but there is no evidence of a dosage effect of the *B2 allele. These data suggest that associations between the CETP gene and lipid phenotypes can be population specific. Further, they suggest that such associations are mediated in some way by gender.

Genetic diversity in the Caucasus.

Abstract: We report genetic variation in the Caucasus, a region showing extreme linguistic differentiation. Spatial autocorrelation analysis of 31 alleles in 793 samples and maps of interpolated allele frequencies show significant geographic structure, but the patterns are clinical for only a few alleles. Many gene frequency distributions are patchy, most likely because of population subdivision and isolation by distance. Genetic boundaries tend to occur in different zones for the different alleles; significant overlap is observed, with boundaries separating different ethnic and linguistic groups. Conversely, the major geographic barriers, including the Caucasus Mountains, seem to have had little influence on the patterns and degrees of genetic differentiation. As a consequence, the genetic structure of Caucasus populations basically reflects restricted gene flow resulting from linguistic or ethnic subdivision. Genetic diversity does not provide evidence for a wavelike population expansion, such as the one associated with demic diffusion of agriculture in most of Eurasia.

Population structure of the Chenchu and other south Indian tribal groups: relationships between genetic, anthropometric, dermatoglyphic, geographic, and linguistic distances.

Abstract: We describe the genetic structure and interrelationships of nine south Indian tribal groups (seven from Andhra Pradesh and two from the adjoining states of Tamil Nadu and Kerala) using seven polymorphic loci (ABO, MN, RH, PGM, ACP, PGD, and LDH). R matrix analysis indicates that the Andhra Pradesh tribes are clustered and that the Kadar and Irula are genetically isolated from them. This dispersion of populations has been explained by the combination of relatively high frequencies of the alleles RH D and MN M in the Kadar and the relatively high proportions of the allele PGM*2 in the Irula. The Mahaboobnagar Chenchu subgroup is isolated from other Telugu-speaking groups because of high frequencies of the PGM*1 and ACP*A alleles. The regression of mean per locus heterozygosity (H) on distance from the gene frequency centroid (rii) reveals considerable levels of external gene flow among the Lambadi, the Yerukula, and the two Chenchu subgroups and more homogeneity in the Kolam, Koya, Yanadi, Irula, and Kadar. Mantel statistics were used to assess the relative effects of nonbiological processes (i.e., language and geography) on the morphological and genetic patterns of these subdivided populations. The significance of correlations was determined between different data sets (genetic, dermatoglyphic, anthropometric, geographic, and linguistic) at three levels involving nine, six, and five populations. Although multiple correlation analysis reveals significant combined effects of geography and language on genetics, anthropometrics, and dermatoglyphics, highly significant partial correlations suggest strong effects of geography on both anthropometry and genetics. Our analysis indicates that geographic factors have an overwhelming effect on the genetic differentiation of the south Indian tribal groups.

Genetic characterization of American and Western Samoans.

Abstract: The Samoan islands were politically separated into American Samoa and Western Samoa in the early 1900s. Economic modernization is far more extensive in American Samoa. However, the Samoan archipelago has maintained a remarkable degree of sociocultural homogeneity, including intermarriage. The sociocultural exchanges presumably led to genetic homogeneity between the two Samoas. Detailed genetic comparisons and characterizations of Samoans are scanty, however. As part of a multidisciplinary study of modernization and cardiovascular risk factors in adults, we analyzed nine hypervariable nuclear DNA (HVR) and four serum protein polymorphisms in the two Samoan groups. The average heterozygosities at both DNA and serum protein loci are comparable in the two groups. As expected, the HVR loci reveal a high degree of variability (heterozygosity 30-87%) compared with the serum protein loci (heterozygosity 1-52%). A large proportion of alleles at the HVR loci, ranging from 50% to 100%, are shared between American and Western Samoa. With the exceptions of the D1S80 locus in American Samoa and the D13S118 locus in Western Samoa, the genotype distributions at all loci conform to their respective Hardy-Weinberg expectations. Sporadic occurrence of the F13B*2 allele at the F13B locus in Samoans indicates a low level of European admixture because this allele is unique to Europeans. The calculated zero values of kinship coefficients and standard genetic distances indicate minimal population differentiation between the two Samoan groups.

Hereditary disorders in the French Canadian population of Quebec. I. In search of founders.

Abstract: Twenty-eight hereditary disorders are known to cluster in at least one region of Quebec, 24 of them in regions east of Quebec City, including 20 in the northeastern part of the province. Genealogies were reconstructed to identify the probable origin of 21 of these 28 disorders present in the French Canadian population. The results showed that most of the disorders were brought to Nouvelle-France by settlers coming from France in the seventeenth century. Only 249 of the 8483 settlers in Nouvelle-France contributed, as common founders, to these genealogies. The contribution of the province of Perche was significantly higher than expected from its relative weight to the founding nucleus of the French Canadian population in 19 disorders. Furthermore, 34 of the 48 different common founders from Perche were found in more than one disorder.

Founder Effect: Assessment of Variation in Genetic Contributions among Founders

Abstract: We present a Monte Carlo method for determining the distribution of founders' genetic contributions to descendant cohorts. The simulation of genes through known pedigrees generates the probability distributions of contributed genes in recent cohorts of descendants, their means, and their variances. Genealogical data from three populations are analyzed: the Hutterite population of North America, the island population of Sottunga from the Aland archipelago, and the large Utah Mormon population. Two applications of the Monte Carlo method are presented. First we investigate the relative opportunity for founder effect in the three populations, which have dissimilar pedigree structures and dissimilar disease gene frequencies. Second, we measure the reproductive success of population founders in terms of the number of genes they contribute to a cohort some number of generations descendant and compare the effects of polygyny versus monogamy on reproductive success. The distribution of Hutterite founder contributions describes the context for a classic founder effect. Hutterite founders have a higher probability of leaving no genes in the population (72%) than Sottunga (48%) and Mormon (48%) founders. However, founder genes that survive among Hutterite descendants do so in larger numbers on average than founder genes in the other two populations. Greater variation among monogamous Hutterite founders compared with Mormon polygynous founders demonstrates that polygyny alone does not maximize the variance in reproductive success; other population characteristics are at least as important for determining variability among individuals in their genetic contributions to a gene pool. Our findings make it difficult to appreciate the reproductive advantage of polygyny in the Mormon population. Although the expected gene contributions and their variances were larger for polygynous founders compared with other Mormons, the main effect of polygyny was to increase the probability that any polygynist left a few genes among descendants. Furthermore, only 12% of the variation in the genetic contributions of Mormon founders is explained by their number of offspring. We conclude that shallow genealogical data (from one or a few generations) provide a poor measure of long-term reproductive success.

Preliminary Report on the Paleodemography of the K2 and Mapungubwe Populations (South Africa)

Abstract: Paleodemographic studies have seldom been attempted in sub-Saharan Africa. The Mapungubwe complex of sites in northern Transvaal (A.D. 970-1200) has yielded enough skeletal material to warrant such an investigation. The skeletal collection consists of 109 individuals (97 from K2 and 12 from Mapungubwe itself). Because the sites are extensive and their complete excavation impractical, only reconstruction of the population dynamics, not the population size, was possible. There were 81 child and juvenile skeletons (below 15 years of age) and 7 male, 5 female, 4 possible male, and 4 possible female adult skeletons. Eight adult skeletons were too fragmentary to warrant even tentative sex diagnoses. Either age-specific burial practices resulting in the surplus of child skeletons, unusual child mortality, or a state of substantial natural increase must be the explanation for this age distribution. The hypothesis of the natural increase can be partly tested by using an appropriate correction to the life table. The life table corrected for r = 2.5% has a newborn life expectancy of 18.93 +/- 1.79 years and a survivorship to 15 years of 41.66% +/- 3.91. The population pyramid derived from this life table compares well with data on some third world populations observed earlier this century. The fertility rate required to maintain the natural increase under such mortality conditions is high but comparable to that of some historical populations. High positive natural increase would indicate an economically successful population.

Mountains and genes : population history of the pyrenees

Abstract: The Pyrenees Mountains rise between France and Spain. At their western end live the Basques, one of the oldest populations in Europe. All the available genetic information (gene frequencies of blood groups, serum proteins, red cell enzymes, and HLA antigens) on Pyrenean populations has been gathered and subjected to two kinds of analysis: a discrete approach, in which eight separate populations have been defined according to linguistic and geographic criteria to compute genetic distances between them; and a continuous principal components analysis on gene frequencies interpolated to a regular grid. In the first approach the Pyrenean samples have also been compared to other Western European populations. Our results show that the Basque population is most genetically differentiated with respect to other Pyrenean and Western European populations. There is a strong genetic gradient along the mountain range (i.e., in an east-west direction); thus the mountains have not acted as barriers to gene flow. A Catalan-speaking sample, the Cerdanya, is slightly detached from its neighbors and seems closer to other European populations. This genetic picture together with linguistic, paleoanthropological, and archeological data points to a Mesolithic (or older) differentiation of the Cantabrian ancestors of the Basques. Moreover, the Basque genetic features are found in the northern slope of the Pyrenees far beyond the present Basque linguistic boundaries, in accordance with the most recent hypotheses on Pyrenean historical linguistics. The genetic consequences of the arrival of the first Indo-European-speaking peoples in the Iberian Peninsula are also studied; no clear genetic trace has been left of that population movement, except perhaps for the Cerdanya, an eastern valley that affords a passage between north and south.

Genetic structure of the Utah Mormons: comparison of results based on RFLPs, blood groups, migration matrices, isonymy, and pedigrees.

Abstract: The genetic structure of the Utah Mormon population is examined using 25 blood group and 47 RFLP alleles obtained from 442 subjects living in 8 geographic subdivisions. Nei's GST was 0.013 (p 0.4) for the blood group data, showing that only 1% of the genetic variance in this population can be attributed to subdivision effects. A comparison of intersubdivision distance matrices based on blood groups, RFLPs, migration matrices, isonymy, and pedigrees shows that genetic distances have relatively low and nonsignificant correlations with the other three types of data. However, the correlations based on RFLPs are considerably higher than those based on blood groups. Relationship matrices based on interindividual allele sharing were compared with known genealogical kinship coefficients between each pair of individuals. The correlation between the blood group and RFLP relationship matrices was small but marginally significant using the Mantel test (r = 0.014, p < 0.06). The RFLP relationship matrix correlated more highly with genealogical kinship than did the blood group relationship matrix (r = 0.023, p < 0.0001 and r = 0.012, p < 0.001, respectively). These correlations increased by approximately one order of magnitude when pairs of subjects having zero kinship coefficients were excluded. These results show that genetic distances derived from RFLPs correlate more strongly with other types of kinship than do distances based on blood groups. This probably reflects the fact that RFLPs are more neutral, have frequencies that are more accurately estimated, and contain more information about DNA sequence variation.

Reduced variability in Y-chromosome-specific haplotypes for some Central African populations.

Abstract: Only 7 nonrare haplotypes concerning Y-chromosome-specific TaqI fragments recognized by DNA probes p49f and p49a were encountered in 433 individuals belonging to 7 populations living in central Africa. Most of the haplotypes (77.7%) are characterized by the allelic combination A1,C0,D0,F1,I1 (haplotype IV). The degree of variability displayed by these sequences is low in the African population studied, compared with Europeans, probably because of the recent common origin of the Bantu-speaking populations studied and the common practice of male polygamy in Africa.

Twin resemblance in somatotype and comparisons with other twin studies.

Abstract: Twin resemblance in somatotype components was considered in 28 male and 34 female monozygotic (MZ) twin pairs and 19 male and 21 female dizygotic (DZ) twin pairs, 9.3-23.5 years of age. The Heath-Carter anthropometric somatotype method was used. Mean somatotypes of male twins and female twins did not differ, whereas male twins were significantly more mesomorphic than female twins. Twin resemblance was evaluated in two ways: first, treating each somatotype component independently of the other two (as in earlier twin studies), and, second, looking at resemblance in each somatotype component after statistically controlling for the other two components (thus treating the somatotype as a composite). Intraclass correlations were consistently higher in MZ than in DZ twins of both sexes, and within-pair variances were consistently lower in MZ than in DZ twins of both sexes. However, after controlling for the effects of the other two somatotype components, within-pair variances of male MZ and DZ twins for each somatotype component did not differ. In general, Heath-Carter anthropometric somatotype components show (1) significant resemblance in MZ and DZ twins within each sex, although the degree of resemblance is altered in male twins when a different analytic strategy is used, (2) no sex difference in degree of resemblance, and (3) greater resemblance within MZ twin pairs than within DZ twin pairs. These results are compatible with the presence of genetic variation affecting physique in adolescents and young adults.

Religious differentials in postfamine marriage patterns, Northern Ireland, 1840-1915. I. Demographic and isonymy analysis.

Abstract: During the Irish famine of 1846-1851 there were an estimated 1.0 million excess deaths, the migration of 1.3 million persons, and 300,000 averted births. To assess the influence of population changes at the local level in Ulster, decennial census records were analyzed for the Barony of Upper Ards, County Down, from 1841 to 1911. Data on marriages contracted in the four Roman Catholic, five Presbyterian, and eight Episcopalian congregations also were abstracted from civil parish registers for the period 1840-1915 and were used to calculate levels of random and nonrandom inbreeding through time by isonymy analysis. In the prefamine census of 1841 the total population of the Upper Ards was 16,964. From 1841 to 1911 population numbers decreased by 44.5%, with a consistent surplus of females in all parishes throughout the study period. Both population density and the number of persons per dwelling declined at equivalent rates, resulting in increasingly dispersed patterns of settlement. There was a marked overall increase in nonrandom inbreeding (Fn) in the immediate postfamine period, which was sustained throughout the nineteenth century before declining during 1900-1915. However, significant heterogeneity was observed in the Fn values calculated, both between and within each of the three main religious denominations, indicating differential local responses to marriage partner choice in the postfamine years. The observed changes are not compatible with a simple model of reduction in mate availability under conditions of population decline. Instead, they can most convincingly be explained in terms of a specific population response to the subsistence crisis initiated by the famine.

Recent fertility decline in Dariusleut Hutterites: an extension of Eaton and Mayer's Hutterite fertility study.

Abstract: A church book that has been routinely updated by the Dariusleut Hutterites enabled us to update some fertility tables presented by Eaton and Mayer in the 1950s. The age-specific (nuptial) fertility rates and the total fertility rates (TFRs) were calculated for every 5-year period from 1901-1905 to 1981-1985. Our calculations for Dariusleut, one of the three sects of the Hutterites, gave slightly lower age-specific nuptial fertility rates before 1951 compared with the figures given by Eaton and Mayer (1953) for all Hutterites in the corresponding time periods. The recent decline in Hutterite fertility, especially at higher maternal ages, was confirmed in this study. The TFR, given as a sum of 5-year-grouped age-specific nuptial fertility rates from 15 to 49 years of maternal age, was higher (8.80-9.83) in the years 1946-1965, but it declined to 8.13 in 1966-1970, to 7.22 in 1971-1975, to 6.39 in 1976-1980, and to 6.29 in 1981-1985. For the age groups 35-39 years and older the age-specific nuptial fertility rate in 1981-1985 decreased by more than 50% compared with the rate during the peak period of 1951-1955. The probability of a married woman having a live birth at each age from 15 to 49 years still peaked around the twentieth year of life, as found by Eaton and Mayer (1953), but it decreased more rapidly from the late twenties among the recently married women, most evidently in their thirties.

Efficacy of a composite biological age score to predict ten-year survival among Kansas and Nebraska Mennonites.

Abstract: In 1980 and 1981 Mennonite descendants of a group of Russian immigrants participated in a multidisciplinary study of bi- ological aging. The Mennonites live in Goessel, Kansas, and Hen- derson, Nebraska. In 1991 the survival status of the participants was documented by each church secretary. Data are available for 1009 individuals, 177 of whom are now deceased. They ranged from 20 to 95 years in age when the data were collected. Biological ages were computed using a stepwise multiple regression procedure based on 38 variables previously identified as being related to survival, with chronological age as the dependent variable. Standardized re- siduals place participants in either a predicted-younger or a predicted- older group. The independence of the variables biological age and survival status is tested with the chi-square statistic. The signifi- cance of biological age differences between surviving and deceased Mennonites is determined by t test values. The two statistics provide consistent results. Predicted age group classification and survival status are related. The group of deceased participants is generally predicted to be older than the group of surviving participants, al- though neither statistic is significant for all subgroups of Menno- nites. In most cases, however, individuals in the predicted-older groups are at a relatively higher risk of dying compared with those in the predicted-younger groups, although the increased risk is not always significant.

Hereditary disorders in the French Canadian population of Quebec. II. Contribution of Perche.

Abstract: In our previous paper (De Braekeleer and Dao 1994) we showed that most of the hereditary disorders present in the French Canadian population of Canada cluster in eastern Quebec. Furthermore, the disorders probably were brought to Nouvelle-France in the seventeenth century by migrants coming from Perche, France. Here, the analysis of several historical, social, and demographic factors shows that, rather than migrants coming from other French provinces, migrants from Perche came from a limited area and settled in eastern Quebec, preferentially on the north shore of the St. Lawrence River. They arrived earlier than the other migrants and had a larger descendance. However, only a limited number of migrants from Perche were found in the founding nucleus of the hereditary disorders. Further analysis shows that the social system had major consequences on migration, marriage, kin network, and family behavior. Therefore the presence and the high frequency of most of the hereditary disorders in the French Canadian population appear to be the result of founder effect and genetic drift.

Testing hypotheses on processes of genetic and linguistic change in the Caucasus.

Abstract: Extensive genetic diversity exists in the populations of the Caucasus. Various hypotheses on its origin and evolution were tested by comparing genetic, geographic, and linguistic distances. Seventeen polymorphic loci and 107 localities were considered, and Mantel tests of matrix association were carried out. Genetic differences correlate more with linguistic than with geographic distances; but when populations are grouped by the language spoken, this correlation loses significance, whereas genetic and geographic distances between groups appear significantly associated. Hypotheses that classify North and South Caucasian languages into distinct families or that treat all North Caucasian languages as independent linguistic entities fail to account for genetic variation better than simpler models. We interpret these results as evidence for an evolutionary process in which linguistic and genetic divergence has resulted from population subdivision and from processes of elite dominance, that is, language replacement not associated with major migratory movements.

Genetic characterization of the Cayapa Indians of Ecuador and their genetic relationships to other Native American populations.

Abstract: One-hundred sixty-four Cayapa Indians living in the Esmeraldas Province (northwest Ecuador) were studied for several erythrocyte genetic markers (ACP1, ADA, AK1, CA2, ESD, GLO1, G6PD, PGD, PGM1 subtyping and thermostability, PGM2, SODA, and HB). The Cayapa show allele frequencies typical of those of South American Indians. The absence of the CA2*2, G6PD*A, G6PD*A-, HBB*S, and HBB*C alleles and the low PGM1*1A and PGM1*2A and high PGM1*1B allele frequencies indicate that very little (no more than 2%), if any, genetic admixture has occurred with the black community living in the same area. Correspondence analysis was used to study the genetic relationships between the Cayapa and other linguistically defined Amerind populations and between the Amerinds and the other two native American groups, the Na-Dene and Eskimo-Aleut. The results of this analysis, obtained on the basis of some erythrocyte and serum markers and some blood group systems, show (1) the close affinity between the Cayapa and other South American populations, (2) the absence in the Amerind group of a clear-cut correspondence between linguistic classification and genetic relatedness, and (3) the evident distinctiveness of the Amerinds from other native American people.

Differential fertility as a mechanism maintaining balanced polymorphisms in Sardinia.

Abstract: Women's fertility, gathered from the 1961 Italian population census, and estimates of heterozygote frequencies for thalassemia and G6PD deficiency (Siniscalco et al. 1961, 1966) in 52 Sardinian villages were examined to study at the population level the mechanisms that have maintained the stability of these polymorphisms over long periods. Sardinian villages were classified according to low or high frequency of heterozygotes, and the reproductive behavior of the women living in these areas was analyzed. A high mean number of children per woman and a low percentage of women without children with a high heterozygote frequency was demonstrated. The observed differential fertility and sterility were interpreted as being the result of different numeric ratios within each area between normal homozygous and heterozygous women, who were less and more resistant, respectively, to malarial infection, according to Haldane's theory. The effect of differing degrees of malaria on fertility rates has been demonstrated previously (Zei et al. 1990). To account for the effect of the genetic and epidemiological composition of an area on reproductive behavior, we classified data on women's fertility and sterility by heterozygote frequency level and malarial morbidity level. A combined and direct effect of inherited and acquired immunities on fertility and sterility rates was shown. The level of endemicity in an area may contribute to decreasing or increasing fitness, which is already influenced by the stable balanced polymorphisms.

Genetic studies in Cameroon : mitochondrial DNA polymorphisms in Bamileke

Abstract: In two population samples of 77 Bamileke (Bantu sensu lato) and 18 Bakaka (Bantu sensu stricto) from southwestern Cameroon, the mtDNA RFLPs for the HpaI, HaeII, MspI, AvaII, and HincII enzymes were studied. Two of the MspI morphs had not been reported before. Six new types were found, four of which represent new combinations of previously described morphs. The AvaII morph 3 was found in association with the "African" HpaI morph 3. This finding is in line with previous observations in Negroids and demonstrates the usefulness of this combination as an indicator of black African ancestry. Two differences were noted between the groups: a lower frequency of HpaI morph 3 and a higher frequency of HaeII morph 4 in the Bakaka with respect to the Bamileke (0.44 versus 0.62 and 0.17 versus 0.03, respectively). The importance of these differences could not be evaluated because the Bakaka sample was too small. Nevertheless, because the Bamileke show a relatively low frequency of mtDNA type 1 (2.1.1.1.-) and high frequencies of mtDNA types 2 (3.1.1.1.3.-) and 7 (3.1.1.1.1.-), they can be placed with the other Negroids so far examined, but they are closer to the Senegalese than to the Bantu from South Africa. In comparing the Bamileke and the Bantu, mtDNA type 3 (3.1.1.2.2.-) appears particularly discriminative because it is present in all the Bantu subgroups examined but not in the Bamileke. mtDNA type 39 (2.1.4.1.1.-), which was observed only in the Bamileke, might be considered likewise discriminative, although to a lesser degree.

Obesity in Pima Indians: genetic segregation analyses of body mass index complicated by temporal increases in obesity.

Abstract: During the past half-century the prevalence of obesity in developed countries has increased greatly. Such short-term changes in prevalence must be environmentally determined, but genes can mediate response to environmental change, for example, through variable gene penetrance and expression. Obesity differences between bith cohorts complicate the interpretation of phenotypic comparisons between generations that span periods of change. Genetic segregation analyses of the body mass index in 618 Pima Indian nuclear families (2 generations) identified recessive major gene inheritance, which is the same pattern of transmission that has been found in several other populations. However, within-birth-cohort analyses of siblings (one generation) uniformly supported codominant major gene inheritance with no polygenic heritability. For untransformed data transmission probabilities were Mendelian in the later-born cohort and in the combined sample of siblings. After transformation to remove skewness, transmission probabilities were Mendelian only in the earlier-born cohort (i.e., those siblings born before a period of marked temporal increase following World War II). A higher penetrance of codominant obesity susceptibility genes in the younger generation would result in some genetically obese individuals who have no affected parents, thus simulating recessive inheritance. Taken together, the results of these analyses suggest that the recessive pattern we identified in the Pima Indian nuclear families could be accounted for by temporal changes in penetrance of codominant obesity-predisposing genes. By implication, more modest temporal increases in white and black populations could in part account for the recessive pattern of inheritance described by several investigators.